The recovery of walking is one of the main goals of patients after a neurological impairment (including stroke, multiple sclerosis, cerebral palsy and spinal cord injury (SCI)) as limitations in mobility can adversely affect most activities of daily living. Following a neurological injury, there is often impaired control of balance, paralysis, or weakness of lower extremity muscles including commonly those that activate the ankle. This often has a substantial adverse impact on walking. Specifically, individuals may suffer difficulties supporting their body weight during the stance phase, or shifting weight during the transition to swing, or lifting their foot for toe clearance during the swing phase due to the weakness associated with the injury. Gait training can be done    i. with therapist-assisted over ground ambulation (with or without assistive device)    ii. in a Body Weight Supported Treadmill Training (BWSTT) environment, where assistance for the movement of legs and the pelvis is provided manually by a therapist or    iii. by a robotic device (Lokomat, Auto-Ambulator or Gait Trainer), or in water (weight supported environment, with or without a treadmill).Over ground gait training (with or without a Functional Electrical Stimulation (FES) orthosis) can only be used for individuals with already able to support body weight in an upright position.
BWSTT, robotic device gait training and aquatherapy gait training (training in water) can potentially be used to enhance loco-motor abilities in neurologically impaired individuals, as lack of trunk balance and ability to bear weight in an upright position are replaced by the supporting abilities of the device or environment used (harness, exoskeleton or water). But they are not typically used in clinical practice to aid in locomotor training in individuals with motor complete impairments as this training would need specialized, center based, expensive environment (i.e. therapeutic pool, robotic exoskeleton) or is very labor intensive (sometimes requiring 2-3 therapists' sustained effort over long periods of time).
BWSTT with manual or robotic assistance of the legs and the pelvis has been used as a promising rehabilitation method designed to improve motor function and ambulation in people with SCI (Behrman and Harkema 2000; Dietz et al. 1995; Wernig and Muller 1992; Wirz et al. 2005; Dobkin et al. 2006; Field-Fote et al. 2005). However, while BWSTT has been shown to provide improvements in locomotor ability, motor function, and balance for some patients, the current technology used to assist with the training is typically very expensive, requires trained therapists for utilization and can only be used in a rehabilitation center. Several robotic BWSTT systems have been developed for automating locomotor training, including the Lokomat (Colombo et al. 2000) and Gait Trainer (GT) (Hesse and Uhlenbrock 2000).
The Lokomat is a motorized exoskeleton that drives hip and knee motion with fixed trajectory using four DC motors (Colombo et al. 2000). One limitation is that it is difficult to back drive the Lokomat because it uses high advantage, ball screw actuator. The GT rigidly drives the patient's feet through a stepping motion using a crank-and-rocker mechanism attached to foot platforms (Hesse and Uhlenbrock 2000). These robotic systems have their basic design goal to assist patients in producing correctly shaped and timed locomotor movements. This approach is effective in reducing therapist labor in locomotor training and increasing the total duration of training, but shows relatively limited functional gains for some patients (Wirz et al. 2005; Field-Fote et al. 2005). For instance, only 0.11 m/s gait speed improvement is obtained following prolonged training using the Lokomat (Wirz et al. 2005).
FES has been previously used to enhance the quality of gait training whether as an assistive device (FES orthosis for foot drop) or to enhance muscle strength and improve cardiovascular resistance (FES ergometer), thus decreasing gait induced fatigue. FES has also been used extensively in the rehabilitation of individuals with SCI to:
i. improve muscle mass and strength (Frotzler A, Coupaud S, Perret C, Kakebeeke T H, Hunt K J, Eser P. Effect of detraining on bone and muscle tissue in subjects with chronic spinal cord injury after a period of electrically-stimulated cycling: a small cohort study. Swiss Paraplegic Research, Nottwil, Switzerland; Thomas Mohr, Jesper L Andersen, Fin Biering-Sùrensen, Henrik Galbo, Jens Bangsbo, Aase Wagner and Michael Kjaer. Long term adaptation to electrically induced cycle training in severe spinal cord injured individuals. Spinal Cord (1997) 35, 1±16)ii. control spasticity (Maria Knikou, PhD, and Bernard A. Conway, PhD. Reflex Effects Of Induced Muscle Contraction In Normal And Spinal Cord Injured Subjects. Muscle Nerve 26: 374-382, 2002; Daly J., et al. Therapeutic neural effects of electrical stimulation. IEEE Trans Rehabil Eng 4:218-230, 1996; Robinson C. J., et al. Spasticity in Spinal-Cord Injured Patients 0.1. Short-Term Effects of Surface Electrical-Stimulation. Arch Phys Med Rehab 69:598-604, 1988)iii. improve cardiovascular endurance and respiratory function (Puran D Faghri, Roger M Glaser, Stephen F Figoni. Functional Electrical Stimulation Leg Cycle Ergometer Exercise: Training Effects on Carriorespiratory Responses of Spinal Cord Injured Subjects at Rest and During Submaximal Exercise. Arch Phys Med Rehabil 73:1085-1093)iv improve bone mass (Belanger M, Stein R B, Wheeler G D, Gordon T, Leduc B. Electrical stimulation: can it increase muscle strength and reverse osteopenia in spinal cord injured individuals? Arch Phys Med Rehabil 2000; 81(8):1090-1098; McDonald J W, Becker D, Sadowsky C L, Jane J A, Sr., Conturo T E, Schultz L M. Late recovery following spinal cord injury. Case report and review of the literature. J Neurosurg 2002; 97(2 Suppl):252-265) andv. improve body composition (L. Griffin, M. J. Decker, J. Y. Hwang, B. Wang, K. Kitchen, Z. Ding, J. L. Ivy. Functional electrical stimulation cycling improves body composition, metabolic and neural factors in persons with spinal cord injury. J Electromyography and Kinesiol 2008: 1-8).
FES has been postulated to even alter neuronal control, altering central nervous system plasticity and improving functional tasks performance (Richard K. Shields and Shauna Dudley-Javoroski. Musculoskeletal Plasticity After Acute Spinal Cord Injury: Effects of Long-Term Neuromuscular Electrical Stimulation Training J Neurophysiol 95: 2380-2390, 2006).
Combining gait training with FES activation of selected muscles involved in stepping has been already achieved and there are several commercially available FES driven orthosis for utilization in individuals with SCI, mainly to correct foot drop (Bioness L300, Walk Aid). In addition, in clinical practice, therapists are frequently utilizing hand held triggered neuromuscular electrically stimulated (NMES) devices to aid in foot/toe clearing during the swing phase of the gait when working with individuals with neurologic lower limb weakness.